This invention relates to polymeric thickeners which impart highly pseudoplastic behavior to compositions containing same.
Pseudoplastic compositions are compositions whose viscosity varies in accordance to the shear which is applied to said compositions. In many instances, pseudoplasticity is a desirable attribute of a composition. In many emulsion systems, it is desirable for the emulsion to have a high viscosity upon standing in order to best maintain the stability of the emulsion, but to exhibit a substantially lower viscosity when used in order to facilitate such use. For example, many latex paints are formulated to be very viscous on standing in order to maintain a homogeneous dispersion of its components. However, the shear applied to the paint upon spreading or brushing causes the viscosity of said paints to dramatically drop, thereby easing the application of the paint to the substrate. Then, upon removing the shearing force of the spreader, the paint regains its highly viscous nature and does not flow off the surface to which it is applied. Certain food substances, such as mayonnaises, exhibit similar behavior. Emulsions such as salad dressings and mayonnaise are often quite thick and viscous when in their containers; but are easily spread when subjected to the shearing action such as is applied with a knife.
In such systems, it is often desirable to increase the pseudoplasticity of the composition, i.e., to increase the dependence of the composition's viscosity to the shear being applied thereto. Unfortunately, however, most polymeric thickeners do not impart the desired degree of pseudoplastic behavior to the composition. Accordingly, a thickener which does impart very high pseudoplasticity to compositions containing said thickener would be highly desirable.